A reversing valve a type of valve and is a component in a heat pump, that changes the direction of refrigerant flow. By reversing the flow of refrigerant, the heat pump refrigeration cycle is changed from cooling to heating or vice versa. This allows a residence or facility to be heated and cooled by a single piece of equipment, by the same means, and with the same hardware.
Depending on the construction and use of the heat pump, the reversing valve may be driven by the heat pump through the use of a defrost control board, or it may be driven directly by a thermostat (typically from the "O" terminal).
